This invention relates to an axial piston fluid pumping apparatus, and more particularly to such an apparatus which uses a wobble piston, the stroke for which is provided by a swashplate.
Two known types of compressors are the wobble piston type and the swashplate type. The wobble piston type is exemplified by U.S. Pat. No. 3,961,868 issued Jun. 8, 1976, to Droege, Sr., et al. for "Air Compressor". Such a compressor uses a piston whose head has a peripheral seal that seals with a cylinder bore. The piston rod is mounted radially on a crankshaft. The piston includes no joints or swivels. As a result, the piston head is forced to "wobble" in two dimensions within the cylinder bore as it is driven by the crankshaft.
The swashplate type compressor uses a plurality of axial cylinders arranged in a circle about a drive shaft. A swashplate is inclined relative to the shaft axis such that the plate gyrates as the drive shaft is rotated. Pistons are mounted in each of the cylinders. The ends of the piston rods are connected to elements that slide over the surface of the swashplate as the swashplate rotates. The result is that the centerline of the piston head is moved solely in an axial direction as the pistons are stroked within the cylinders. An example of such an axial piston swashplate compressor is found in U.S. Pat. 5,362,208 issued Nov. 8, 1994 to Inagaki, et al. for "Swashplate Type Compressor". Another example is U.S. Pat. No. 4,776,257 issued Oct. 11, 1988, to Hansen for "Axial Pump Engine". In the Hansen Patent, the centerline of the piston heads are inclined relative to the centerline of the cylinder bore, but the piston heads are moved only along the piston head centerline in one direction.
The present invention combines the wobble pistons normally used in radial piston pumps with the swashplate normally used in axial piston pumps. The result is a simple and effective fluid pumping apparatus.